Cellular Physiology: Solutions and Transport Part 2

Study Notes

A solution is a homogeneous mixture of two or more components, consisting of a solvent and solutes.
The solvent is the dissolving medium, while solutes are the components present in smaller quantities.
Intracellular fluid includes nucleoplasm and cytosol, whereas interstitial fluid refers to fluid surrounding cells.

Cellular membranes are selectively permeable, regulating the movement of substances into and out of the cell.
Transport methods are categorized as passive, requiring no energy, or active, which requires metabolic energy from the cell.

The plasma membrane selectively allows certain materials to pass while excluding others, controlling cellular movement.

Diffusion is the tendency of particles to evenly distribute, moving from high to low concentration (down a concentration gradient) due to kinetic energy.
Simple diffusion allows lipid-soluble materials or small particles to pass without assistance.
Osmosis refers to the passive diffusion of highly polar water across the plasma membrane.
Facilitated diffusion requires a protein carrier for substances to move down the concentration gradient without energy.
Filtration involves forcing water and solutes through a membrane using hydrostatic pressure, driven by a pressure gradient, allowing different sizes to be filtered.

Active transport facilitates movement of substances that cannot diffuse due to size, lipid solubility, or concentration gradients.
Solute pumping transports amino acids, sugars, and ions via protein carriers energized by ATP, often against concentration gradients (e.g., sodium-potassium pump).
Bulk transport includes exocytosis, which moves materials out of the cell via membranous vesicles that merge with the plasma membrane to release contents.
Endocytosis involves the engulfing of extracellular substances in a membranous vesicle, with types including phagocytosis (cell eating) and pinocytosis (cell drinking).